Control apparatus



Dec. 4, 1945.

D. M. BORDEN CONTROL APPARATUS Filed April 13, 1944 IN VEN TOR. flat/a4Mzar'jerz &

HTTdFlVEYS,

' Patented Dec. 4, 1945 7 2,390,043 common ArrsaA'rUs David M. Borden,Royal Oak, Mlch.. assignor to Chrysler Corporation, Highland Park,Micln, a

corporation of Delaware Application April 13, 1944, Serial No. 530,927

Claims.

This application relates to an apparatus for controlling a supercharger.More specifically it relates to an apparatus for preventing asupercharger from reaching or exceeding the pumpin limit.

It is known that superchargers, particularly those of the axial type,may under certain conditions reach a condition known as pumping limit,at which the flow of gas through the machine is unsatisfactory. Thevelocity or the g s passin into the supercharger becomes too low for therotational speed of the blades and associated parts. The gas meets theblades at too great an angle of attack, aerodynamic flow is interrupted,and the supercharger stalls. This condition produces noises andvibration and pulsations that may cause physical failure of the parts.

If a supercharger is to be used only at one altitude, it is notdifiicult to design it so that it may be operated satisfactorily withinthe pumping limit. However, if the supercharger is to be used atdifferent altitudes as is the case when it is part of an aircraft powerplant, the greatly varying intake pressures cause pumping limit to occurunder varying conditions, and it is very difficult to make thesupercharger operate within the pumping limit at all times.

It has been discovered that when pumping limit occurs, there is adisturbance or change in the relation of the pressures of certainregions of the machine. I propose to put this disturbance or change towork to tak the supercharger away from the pumping limit.

An object of the present invention is to provide an improved control fora supercharger, particularly one of the axial type. More specificallythe control is adapted to prevent the supercharger from reaching thepumping limit.

A further object is to produce a control for a supercharger forpreventing the supercharger from reaching or exceeding the pumpinglimit, which control operates directly upon a phenomenon arising at acondition of pumping limit. The advantage in providing a control of thistype is that it is more direct and is less dependent on a maze ofcomplications such as operating characteristics of the supercharger atvarying temperatures and pressures.

Other objects will appear from the disclosure.

In the drawing:

Fig. 1 is a view partially in section and partially in diagrammatic formshowing the invention of the present application; and

Fig. 2 is a developed view of a portion of a blade stage of thesupercharger employed in the present invention.

A supercharger I0 comprises a rotor II and a stationary casing memberl2. Upon the rotor ii is mounted a plurality of blade stages, of whichstages l8 and i4 adjacent a receiving end l5 of the supercharger iii areshown. The stationary member [2 carries a plurality of blade stages ofwhich the first,two stages it and I! adjacent the receiving end l5 ofthe supercharger are shown. The first stationary stage it, or in otherwords, the first stage associated with the stationary easing member i2comprises a plurality of blades Iii. The rotor is driven by a shaft l9projecting from the left end of the supercharger iii as shown in Fig. land is joumalled on bearing means, not

shown, at this end of the supercharger. The left end forms a dischargeportion 20 connected with a line 2| leading to an engine, not shown. Atone point of the line 2| is a'tubular part 22 carrying a spill valve 23.An arm 24 secured to the spill valve 23 is connected to a link. 25connected in turn to a stem 26 on a piston 21. The piston 21 is mountedin a cylinder 28 and is urged to the left, as viewed in Fig. 1, by acoil spring 29 acting between the piston 2'! and between a plate til atthe right end of the cylinder 28. A pressure line 3| having arestriction 32 therein supplies fluid under pressure to the cylinder 28.A line 33 leads from the cylinder 28 to a tubular portion 34 of a casingpart 35. One end of the line 33 is secured in a plug 36 threaded in anopening 3? in the tubular portion 34. A sleeve 38 is fixedly mounted ina bore 39 inthe tubular portion E i and has a flange Ml resting in anenlarged portion ill at the end of the bore 39. The sleeve 38 has a port42 at the opening 37. in the tubular portion 34 and at its opposite sidea port 43 at an opening 44 in the tubular portion 34 at which a drainline 45 is connected. Slidably mounted within the sleeve 38 is a pistonvalve 45 havinga long section 41, a short section 48, and a reducedsection 49 joining the sections 41 and 48. The long section 41 has arounded end 50 which is connected to diaphragm 5i clamped between thecasing part 35 and a mating casing part 52. The diaphragm 5| divides thespace enclosed by the casing parts 35 and 52 into a lower chamber 53 andan upper chamber 54.

A line 55 secured in a plug 56 threaded in an enlarged portion 51 of anopening 58 in the casing part 35 leads from the chamber 53 to a specialblade 59 secured to the stationary casingmember l2 in place of one ofthe regular blades l8 of the first stationary stage l6. The specialblade 59 is at a lesser angle to the axis of rotation of the rotor ii,represented by the dash-dot line 60 at the top of Fig. 2, than are theregular blades I 8. The line 55 is connected to a length wise passage 6|extending from the root of the blade 59 to a midpoint in the blade atwhich point it is connected to a transverse passage 62 opening into aface 63 of the blade 59, which is more cambered than an opposite face 64of the same blade. A line 65 secured within a plug 66 threaded in anopening 61 in the casing part 52 leads from the chamber 54 to a blade l8adjacent the special blade 59. The connection of the line 65 tothe bladeI8 is the same as the connection of the line 55 to the special blade 59,although the former is not shown in Fig. 1. As may be seen in Fig. 2,the line 65 is connected to a lengthwise passage 68in the blade l8terminating in a crosspassage 69 opening into a face 13 of the blade l8,which is more cambered than an opposite face II. The passage 69 is at amidpoint of the length of the blade I6 as is the passage 62 in thespecial blade 59.

It will be apparent that the chambers 53 and 54 are subjectedrespectively to the pressures at the faces 63 and 10 of the blades 59and 18. The relationship of these pressures determines the position ofthe diaphragm 5| and of the piston valve 46. Fig. 1 shows the diaphragmand piston valve in the position which they occupy when' thesupercharger is at rest. At this time the pressure in the chambers 53and 54 are equal since the pressures on the faces 63 and Ill of theblades 59 and I8 are equal. Let it now be assumed that the superchargerI is operating with the rotor II and its blades moving past the blades I3 and 59 in the direction indicated by the arrow 12. The moving bladesexert a force or effect a velocity of the air, tending to cause flow ofthe air in a direction indicated by an arrow 13 transverse to the axisof rotation represented by the line 60; During normal operation of thesupercharger within the pumping limit, the air moves through thesupercharger with a component of flow represented by the arrow 14. Theactual flow of the air is in the direction indicated by the arrows 15.The arrow I shown applied to the one blade l9 has a direction along theface of the blade and the corresponding arrow applied to the specialblade 59 as an arrow somewhat away from the face 63. There are negativepressures developed at these faces .and the negative pressure at theface 63 is somewhat greater than that at the face 10. Thus the negativepressure in the chamber 53 is somewhat greater than in chamber 54 andthe piston valve 46 is somewhat lower than its position in Fig. 1, thesection 41 blocking the passage of fluid from the line 33 to the drainline 45. However, when a, condition of stall arises such as is the casewhen the pumping limit of the supercharger I0 is approached or reached,the axial component 14 of the flow of air through the superchargerbecomes materially reduced to an amount represented by an arrow 16.Resultant flow of the air is indicated by the arrows 11. from thecomparison of the arrows I5 and 11,

the direction of flow of the air is at a greater angle to the axis ofrotation of the supercharger represented by the line 60. Although thedirection of flow is somewhat away from the face I0 of the blade Hi,this is not suflicient to cause a separation of flow of air along thisface and there As is evident is an appreciable negative pressure at thisregion. However, the direction of flow is sumciently away from the face63 of the special blade 59 that a separation of flow takes place and thenegative pressure is so reduced at the face 63 that it becomes less thanthat at the face 16. Thus when the condition of stall arises there is areversal of pressure conditions at the faces 63 and 10 of the specialblade 59 and the regular blade l8. This reversal of conditions isreflected in the chambers 53 and 54 for now the negative pressure of thechamber 54 is greater than that of the chamber 53. As a result, thediaphragm 5| and the piston valve 46 move upwardly causing the pistonvalve section 41 to uncover the port 43. Thus fluid may escape from theline 33 past the reduced section 49 of the piston valve 46 into thedrain line 45. This reduction in pressure causes a shifting of thepiston 21 in the cylinder 23. When there was no condition of stall andconsequently no flow of fluid from the line 33 to the drain line 45 thepressure in the cylinder 28 was at a maximum. Consequently the piston 21was at an extreme position to the right, acting through the stem 26, thelink 25, and the arm 24 to hold the spill gate 23 in the closedposition. With the arising of a condition of stall the passage of fluidfrom the line 33 to the drain line 45 reduces the pressure in thecylinder 28 allowing the piston 21 to move to the left. This leftwardmovement acts through the stem 26, the link 25, and the arm 24 to openthe spill gate 23 and consequently. This reduction in pressure bringsabout a, removal of the condition the flow of air through thesupercharger is insumed and the diaphragm 5| and the piston valve 46move back to the position of Fig. 1 in which the piston valve section 41covers the port 43 thereby blocking flow of fluid from the line 33 tothe drain line 45. This action causes an increase in the pressure of thefluid within the cylinder 28, and the piston moves to the right closingthe spill gate 23.

It will be apparent from the foregoing description that a new apparatushas been developed for keeping a supercharger away from the pumpinglimit or for preventing it from exceeding the pumping limit. The deviceoperates directly from conditions arising in the supercharger onapproach or arrival of pumping limit and involves the use of reversal inthe relation of pressures at a regular stationary blade and at anotherstationary blade at an angle different from that of the regular blade.The drawing shows that the regular blade, the pressur of which isemployed in the operation of the device, is adjacent the special bladebut this is for the purpose of illus- I the supercharger. Althoughlocation of the special blade at this point may be desirable andadvantageous, it is not an absolute necessity, for the same change inthe flow may occur at anotherblade stage. I

The intention is to limit the invention only within th scope of theappended claims.

I claim:

1. Apparatus for keeping within the pumping limit a supercharger havingrotary and regular stationary blades, comprising a special stationaryblade mounted on the supercharger adjacent the aforementioned regularstationary blades and being at a lesser angle to the axis of rotationthan that of the regular stationary blades, a spill valve in thedelivery line of ,the supercharger, means responsive to change in therelation of the pressures at a point of the special blade and acorresponding point of one of the regular startionary blades due toapproach or arrival of the pumping limit, and means connecting the spillvalve and the aforesaid means for causing approach or arrival of thepumping limit to increase the opening of the spill valve.

2. Apparatus for keeping within the pumping limit a supercharger havingrotary and regular stationary blades, comprising a special stationaryblade mounted on the superchargeradjacent the aforementioned regularstationary blades and being at a diflerent angle to the axis -ofrotation from that of the regular stationary blades, a spill valve inthe delivery-line of the supercharger, means responsive to change in therelation of the pressures at a point of the special blade and acorresponding point of one of the regular stationary blades due toapproach or arrival of the pumping limit, and means connecting the"spill valve and the aforesaid means for causing approach or arrival ofthe pumping limit to increase the opening of the spill valve.

3. Apparatus for preventing th reaching or charger adjacent theaforementioned regular sta- 4 point of the stationary blade stagingadjacent tionary blades and being at a lesser angle to the axis ofrotation than that of the regular stationary blades, a spill valve inthe delivery line of the supercharger, means responsive to reversal inthe difference of the pressures at the special blade and one of theregular stationary blades due to approach or arrival of the pumpinglimit, and means connecting the spill valve and the aforesaid means forcausing approach or arrival of the pumping limit to increase the openingof the spill valve.

4. Apparatus for keeping within the pumping limit a supercharger havingrotary and stationary blades, comprising a special stationary blademounted on the supercharger adjacent the aforementioned regularstationary blades and being at a different angle to the axis of rotationfrom that of the regular stationary blades, a spill valve in thedelivery line of the supercharger, means responsive to reversal in thediiference of the pressures at a point of the special blade and acorresponding point of one of the regular sta-- tionary blades due toapproach or arrival of the pumping limit, and means connecting the spillvalve and the aforesaid means for causing approach or arrival of thepumping limit to increase the opening of the spill valve.

5. Apparatus for keeping within the pumping limit a supercharger havingrotary and regular stationary blade stages alternately placed withrespect to one another comprising a special stationary blade mountedadjacent a regular stationary blade staging near the inlet of thesupercharger at a lesser angle to the axis of rotation than that of thestationary blade staging adjacent which it is mounted, a spill valve inthe delivery line of the supercharger, and means responsive to change'inthe relation of pressures at a point the special blad and acorresponding which the special blade is mounted due to approach orarrival of the pumping limit for increasing the opening of the spillvalve.

DAVID M. BORDEN.

